Institute for Diabetes and Obesity
Institute for Diabetes and Obesity
News Article | April 28, 2017
Researchers at the University Medical Center of Johannes Gutenberg University Mainz and the German Research Center for Environmental Health, Helmholtz Zentrum München have discovered that too much of the oncogene Bcl-3 leads to chronic intestinal diseases. They describe in Nature Communications exactly how it throws the immune system off-balance. Chronic intestinal disorders such as ulcerative colitis and Crohn's disease are caused by the body's own immune defense system. Sufferers frequently experience episodic symptoms such as abdominal pain, cramps, and diarrhea. Researchers are still trying to identify the precise underlying origins of these problems. A team led by Dr. Nadine Hövelmeyer and Professor Ari Waisman of the Mainz University Medical Center in collaboration with Dr. Elke Glasmacher of Helmholtz Zentrum München has discovered a new mechanism that causes intestinal inflammation. "With the help of our cooperation partners, we were able to demonstrate that the level of the Bcl-3 protein, which also plays a role in the development of various cancerous diseases, is elevated in the intestinal tract of colitis patients and is indeed a trigger of the disease," said Dr. Nadine Hövelmeyer, head of the work group at the Mainz-based Institute for Molecular Medicine. According to the study, Bcl-3 develops its effect on intestinal health through interaction with the so-called regulatory T-cells (Tregs). Their main task is to prevent overreaction of the immune system and to develop a level of tolerance towards the body they serve. "We were able to demonstrate that Bcl-3 suppresses the activation of Tregs by preventing the necessary genes from being read," explained Dr. Elke Glasmacher, head of the team at the Institute for Diabetes and Obesity in Munich. "Bcl-3 interacts with the transcription factor p50, which is otherwise responsible for activation, and blocks it." "Consequentially, the regulatory T-cells remain passive, the immune system is no longer regulated, and inflammatory processes begin to take place. Experiments using various models have revealed that elevated quantities of Bcl-3 cause certain cells to migrate to the intestines, where they trigger a severe inflammatory response," Dr. Sonja Reissig, lead author of the publication and research associate at Mainz University Medical Center, pointed out. "The results represent a major contribution towards our understanding of chronic intestinal inflammation and hopefully over the long-term will help us discover aspects that we can target with new therapies," concluded Hövelmeyer. Her colleague Professor Ari Waisman, Director of the Institute for Molecular Medicine at the Mainz University Medical Center, added: "We are currently focusing on the search for new active agents that will prevent the interaction between Bcl-3 and p50, thus maintaining normal Treg functionality." Reissig, S. et al. (2017): Bcl-3 Inhibits NF-κB Gene Activity in Regulatory T cells and Modulates their Suppressive Capacity. Nature Communications, DOI: 10.1038/NCOMMS15069
Hernandez-Garzon E.,Cajal Institute |
Hernandez-Garzon E.,CIBER ISCIII |
Fernandez A.M.,Cajal Institute |
Fernandez A.M.,CIBER ISCIII |
And 23 more authors.
GLIA | Year: 2016
Previous findings indicate that reducing brain insulin-like growth factor I receptor (IGF-IR) activity promotes ample neuroprotection. We now examined a possible action of IGF-IR on brain glucose transport to explain its wide protective activity, as energy availability is crucial for healthy tissue function. Using 18FGlucose PET we found that shRNA interference of IGF-IR in mouse somatosensory cortex significantly increased glucose uptake upon sensory stimulation. In vivo microscopy using astrocyte specific staining showed that after IGF-IR shRNA injection in somatosensory cortex, astrocytes displayed greater increases in glucose uptake as compared to astrocytes in the scramble-injected side. Further, mice with the IGF-IR knock down in astrocytes showed increased glucose uptake in somatosensory cortex upon sensory stimulation. Analysis of underlying mechanisms indicated that IGF-IR interacts with glucose transporter 1 (GLUT1), the main facilitative glucose transporter in astrocytes, through a mechanism involving interactions with the scaffolding protein GIPC and the multicargo transporter LRP1 to retain GLUT1 inside the cell. These findings identify IGF-IR as a key modulator of brain glucose metabolism through its inhibitory action on astrocytic GLUT1 activity. GLIA 2016;64:1962–1971. © 2016 Wiley Periodicals, Inc.
Habegger K.M.,University of Cincinnati |
Grant E.,University of Cincinnati |
Pfluger P.T.,University of Cincinnati |
Pfluger P.T.,Institute for Diabetes and Obesity |
And 7 more authors.
Frontiers in Endocrinology | Year: 2011
Objective: Ghrelin, a stomach-derived, secreted peptide, and its receptor (growth hormone secretagogue receptor, GHSR) are known to modulate food intake and energy homeosta- sis. The ghrelin system is also expressed broadly in cardiovascular tissues. Since ghrelin has been associated with anti-inflammatory and anti-atherogenic properties, but is also well known to promote obesity and impair glucose metabolism, we investigated whether ghrelin has any impact on the development of atherosclerosis.The hypothesis that endogenous ghrelin signaling may be involved in atherosclerosis has not been tested previously. Methods and Results: We crossed ghrelin receptor knockout mice (GHSr-/-)intoalow- density lipoprotein receptor-null (Ldlr-/-) mouse line. In this model, atherosclerotic lesions were promoted by feeding a high-fat, high-cholesterol Western-type diet for 13 months, following a standard protocol. Body composition and glucose homeostasis were similar between Ldlr-/- and Ldlr/GHSR-/-ko mice throughout the study. Absence or presence of GHSr did not alter the apolipoprotein profile changes in response to diet exposure on an LDLRko background. Atherosclerotic plaque volume in the aortic arch and thoracic aorta were also not affected differentially in mice without ghrelin signaling due to GHSR gene disruption as compared to control LDLRko littermates. In light of the associations reported for ghrelin with cardiovascular disease in humans, the lack of a phenotype in these loss-of-function studies in mice suggests no direct role for endogenous ghrelin in either the inhibition or the promotion of diet-induced atherosclerosis. Conclusion: These data indicate that, surprisingly, the complex and multifaceted actions of endogenous ghrelin receptor mediated signaling on the cardiovascular system have minimal direct impact on atherosclerotic plaque progression as based on a loss-of-function mouse model of the disease. © 2011 Habegger, Grant, Pfluger, Perez-Tilve, Daugherty, Bruemmer, Tschöp and Hofmann.
Heppner K.M.,University of Cincinnati |
Muller T.D.,University of Cincinnati |
Kirchner H.,University of Cincinnati |
Perez-Tilve D.,University of Cincinnati |
And 5 more authors.
Journal of Endocrinological Investigation | Year: 2013
Background: Ghrelin is a gastrointestinal peptide that promotes a positive energy balance. The enzyme ghrelin O-acyltransferase (GOAT) esterifies an n-octanoic acid to the peptide, thereby enabling ghrelin to bind and activate the ghrelin receptor. Although ghrelin has previously been implicated in the control and maintenance of body core temperature (BCT), the role that this acylation may play in thermoregulation has not been examined. Aim:We aimed to investigate the endogenous role of ghrelin acylation in thermoregulation. Methods: In this study, we exposed mice lacking the enzyme GOAT as well as wild-type (WT) control mice to cold temperatures under ad libitum and fasting conditions. Additionally, we investigated the role of GOAT in metabolic adaptation to cold temperatures by analyzing BCT and energy metabolism in mice with and without GOAT that were progressively exposed to low ambient temperatures (31-7 C). Results: We find that regardless of nutritional status, mice lacking GOAT maintain a similar BCT as their WT counterparts during an 8 h cold exposure. Furthermore, mice lacking GOAT maintain a similar BCT and metabolic adaptation asWT controls during acclimatization to low ambient temperatures. Conclusions: We conclude that the absence of the enzyme GOAT does not play a significant role in maintenance of BCT or metabolic adaptation during exposure to low external temperatures. (J. Endocrinol. Invest. 36: 180-184, 2013).
Barlow J.,University of Plymouth |
Jensen V.H.,University of Plymouth |
Jastroch M.,Institute for Diabetes and Obesity |
Affourtit C.,University of Plymouth
Biochemical Journal | Year: 2016
It has been well established that excessive levels of glucose and palmitate lower glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells. This β-cell 'glucolipotoxicity' is possibly mediated by mitochondrial dysfunction, but involvement of bioenergetic failure in the pathological mechanism is the subject of ongoing debate. We show in the present study that increased palmitate levels impair GSIS before altering mitochondrial function. We demonstrate that GSIS defects arise from increased insulin release under basal conditions in addition to decreased insulin secretion under glucose-stimulatory conditions. Real-time respiratory analysis of intact mouse pancreatic islets reveals that mitochondrial ATP synthesis is not involved in the mechanism by which basal insulin is elevated. Equally, mitochondrial lipid oxidation and production of reactive oxygen species (ROS) do not contribute to increased basal insulin secretion. Palmitate does not affect KCl-induced insulin release at a basal or stimulatory glucose level, but elevated basal insulin release is attenuated by palmitoleate and associates with increased intracellular calcium. These findings deepen our understanding of β-cell glucolipotoxicity and reveal that palmitate-induced GSIS impairment is disconnected from mitochondrial dysfunction, a notion that is important when targeting β-cells for the treatment of diabetes and when assessing islet function in human transplants. © 2016 Authors; published by Portland Press Limited.